• Characterizing wintertime aerosol composition and sulfate formation in Fairbanks, Alaska

      Davey, Ragen; Mao, Jingqiu; Simpson, William R.; Guerard, Jennifer J. (2020-05)
      The citizens of Fairbanks, Alaska are exposed to high levels of air pollutants throughout the winter months, causing the city to violate the Fine Particulate Matter (PM₂.₅) National Ambient Air Quality Standards set in place by the United States Environmental Protection Agency. Previous studies have shown the significant amount of sulfate aerosols particles observed in Fairbanks winters, but the formation mechanism of aerosols containing sulfate in the atmosphere is still unknown. While sulfate aerosol particle formation is commonly driven by oxidants including ·OH, H₂O₂ and O₃, these photochemical species are limited in Fairbanks winter months. This indicates sulfate aerosol particle formation may occur through a nontraditional pathway, and this project investigates one proposed mechanism in which transition metals may catalyze sulfate aerosol particle formation. We collected twelve full diurnal cycles over the winter months of 2019, using a particle-to-liquid sampler (PILS) at hourly time resolution. This PILS instrument creates an aqueous extract containing only the water-soluble components of the aerosol particles. These aqueous extracts were analyzed offline for inorganic and metal concentrations by ion chromatography (IC) and inductively coupled plasma mass spectrometry (ICP-MS). This hourly dataset provides new insights in emissions, chemical processing and their coupling with boundary layer dynamics. We find a strong correlation between hourly sulfate and PM2.5 mass concentrations, but we do not find the strong evidence of transition metal ion (TMI) catalysis on sulfate formation. We also collected twelve sets of aerosol filters using Micro-Orifice Uniform Deposit Impactor (MOUDI) throughout the winter of 2019. These size-resolved filter samples suggest the presence of hydroxymethane sulfonate (HMS) in submicron particles when temperatures are below -30 °C (-22 °F), suggesting a new reservoir for sulfur compounds in Fairbanks winter and warranting further investigation.
    • Glacier contribution to lowland streamflow: a multi-year, geochemical hydrograph separation study in sub-Arctic Alaska

      Gatesman, Tiffany A.; Trainor, Thomas P.; Liljedahl, Anna K.; Douglas, Thomas A. (2017-12)
      Glacier melt affects the geochemical composition of rivers; however, quantifying the glacier contribution to subarctic watershed-scale runoff has attracted limited attention. To estimate glacier contribution, we conducted a 6-year geochemical hydrograph separation study in a geologically heterogeneous glacierized watershed in Interior Alaska. Water samples were collected daily from Jarvis Creek during late April through September. Source waters were collected synoptically each year from rain, snow, baseflow (winter discharge), and the glacier terminus discharge. All samples were analyzed for stable water isotopes and dissolved ion concentrations. Stream surface water samples have large seasonal and inter-annual geochemical variation, however, source waters show distinct chemical signatures allowing the application of a geochemical hydrograph separation model to quantify relative source contribution to lowland streamflow. Considerable inter-annual differences within source water signatures emphasize the importance in informing the model with source waters sampled for each season. We estimated a seasonal average of 35% (20 to 44%) glacier terminus discharge contribution with a daily range of 2 (May) to 80% (September). If glacier contribution was to cease completely, stream discharge would be reduced by 48% and 22% in low and high rainfall summers, respectively. Combined with the documented shrinkage of glaciers, our findings emphasizes the need for further research on glacial wastage effect on subarctic watersheds.
    • Influence of permafrost extent on photochemical reactivity, functional group composition, and geochemical cycling of a subarctic discontinuous permafrost Alaskan watershed

      Gagné, Kristin R.; Guerard, Jennifer J.; Simpson, William; Trainor, Thomas P.; Jones, Jeremy (2020-05)
      Sub-Arctic Alaskan boreal forests are currently extremely susceptible to permafrost thaw caused by increases in atmospheric temperatures in the region. Upon thaw, permafrost soil organic matter can leach out organic matter, nitrogen, and metals. It is important to observe the effects the leaching of permafrost may have on photoreactivity, functional group composition, and metal introduction. Photoproduced reactive oxygen species may affect metal fate and transport through mechanisms such as the photo-Fenton reaction. Functional group analysis allows for differences in natural organic matter source and ability to complex metals throughout a watershed. Additionally, permafrost soils may have the ability to leach in metals through lateral flow of surface waters as observed in other studies. These metals could then complex to organic matter and alter the geochemical cycling within the watershed. Organic matter is a nutrient source, and metals (e.g., As) may increase the toxicity of surface waters through the thaw of permafrost. The influx of sequestered organic matter and metals to surface waters has the potential to drastically alter ecosystem processes. This study observes how permafrost leaching affects water composition, including its overall photoreactivity and functional group composition. The data obtained was then used to observe and deduce conclusions on how permafrost thaw influences surface water photoreactivity and functional group composition. Finally, trace metal analysis was conducted on a whole watershed scale over three years to observe how permafrost influences the geochemical composition of three main thermokarst surface waters with varying degrees of permafrost degradation. Overall, permafrost was determined to be heterogeneous and highly photoreactive both inter- and intra- watershed. Additionally, the functional group composition of surface waters influenced by permafrost thaw was different between summer and winter, indicating that winter is an important period to sample. Due to this change in functional group composition, the photoreactivity of winter samples was higher than summer with regard to the production of reactive oxygen species. Metal concentrations also increased during the winter for lakes identified to be undergoing active permafrost thaw. Finally, this case study found that metal concentration data combined with optical indices provided important information for resolving the possible extent of permafrost beneath thermokarst lakes.
    • Metal(loid) liberation from Alaskan coal combustion products as a function of time in various aqueous media

      Milke, Kyle P.; Guerard, Jennifer J.; Hayes, Sarah M.; Trainor, Thomas P. (2018-12)
      Little is known about the fate and potential toxicity of metal(loid)s that could be leached from coal combustion products by a (sub- )Arctic environment. Several potentially toxic elements are enriched in coal combustion products relative to the average crustal abundance including As, Cu, Se, and Sb. The overarching goal of this project is to examine the release of these and other metal(loid)s from early stage coal ash and fly ash from the University of Alaska Fairbanks (UAF) power plant and identify transformations in the presence of aqueous environmental media. Bioaccessibility experiments performed indicate that early stage coal ash and fly ash contain bioaccessible Cr, As, Se, Sb, and Pb. Bioaccessible concentrations of these commonly known toxic metal(loid)s were found to exceed EPA drinking water and freshwater regulations. Early stage coal ash and fly ash was reacted with 18 MΩ H₂O (control) or simulated rainwater to quantify metal(loid) liberation as a function of time. Leachate pH increased to ca. 12.5 within the first hour. Some metal(loid)s quickly reached the maximum measured concentration and consistently decreased in concentration with time such as Ba, Pb, and Zn, while other metal(loid)s increased in concentration with increased reaction time (e.g., Al, V, and Cr). Leaching behavior of between early stage coal ash and fly ash may be controlled by total initial concentrations present in the two ashes, differences in particle size, dissolution and precipitation reactions, and heterogeneity of metal(loid) distribution within the particles. Early stage coal ash and fly ash were also reacted with reconstituted dissolved organic matter solutions to simulate possible environmental interactions. It was found that for some elements (e.g., Ca), dissolved organic matter did not affect the mobility. Other metal(loid) mobilities were affected by the presence of dissolved organic matter, such as that of Sb, As, Zn, Se, Mo, and V. Some metal(loid) concentrations decreased while others increased with increasing dissolved organic carbon concentrations. Through these experiments, we have obtained a quantitative understanding of the kinetic controls of metal(loid) release from coal ash leaching with various aqueous media. Results from these experiments can help to improve storage and remediation processes for coal combustion products in an effort to protect human and the ecosystem health.
    • Mobility and chemical fate of antimony and arsenic in historic mining environments of Kantishna Hills, Denali National Park and Preserve, Alaska

      Ritchie, Vanessa J. (2011-05)
      Oxidative weathering processes of acid-forming sulfide minerals, such as pyrite (FeS₂), and associated arsenopyrite (FeAsS) and stibnite (Sb₂S₃), can have a significant impact on water quality associated with current and legacy mining operations. Concentrations of toxic metals and metalloids, such as antimony (Sb) and arsenic (As), in acid mine drainage can exceed drinking water quality standards by orders of magnitude. This study provides a detailed hydrogeochemical assessment of the mobility and chemical fate of antimony and arsenic in streams draining from historic antimony mines within Denali National Park and Preserve, Alaska. Antimony and arsenic concentrations in stream water reach up to 720 parts per billion (ppb) and 239 ppb, respectively. Aqueous phase antimony and arsenic speciation was determined using liquid chromatography coupled to an inductively coupled plasma mass spectrometer. Antimony in all water samples is predominantly found as Sb⁵ whereas arsenic was detected as mixtures of As³ /As⁵⁺ . Elevated antimony concentrations extend over 8 km downstream from the source, whereas arsenic quickly attenuates within 1.5 km. High correlation between antimony/arsenic and iron concentrations in fine-fraction streambed sediment indicates that sorption and (co)precipitation with iron (hydr)oxides is an important pathway for the attenuation of antimony and arsenic in natural waters.
    • The temporal and spatial distribution of dissolved and particulate iron over the Gulf of Alaska shelf

      Roberts, Megan Victoria; Aguilar-Islas, Ana M.; Trainor, Thomas P.; Simpson, William (2018-08)
      The Gulf of Alaska (GOA) is a region with contrasting ecosystems where the availability of the essential micronutrient iron (Fe) contributes to the observed productivity. However, knowledge on the temporal and spatial variability of iron species over the GOA shelf is limited. The offshore GOA displays lower annual production and residual nitrate in surface waters throughout the year due to low Fe supply, while high spring production is observed over the shelf due to ample nitrate and Fe supply, but these waters become nitrate limited by mid-summer. Processes promoting the exchange of the Fe rich shelf waters with the nitrate rich offshore GOA waters create favorable conditions for phytoplankton to bloom. Mechanisms for Fe introduction and transport are seasonal freshwater input, alongshore advection from the Alaska Coastal Current eddies, deep wintertime mixing, downwelling, downwelling relaxation, and/or upwelling conditions. Additional Fe sources from subsurface waters and sediment re-suspension can impact Fe distributions. Highly seasonal glacial and river input bring in an abundance of both particulate and dissolved Fe species, which differ in their biological availability. For example, dissolved Fe (DFe) is much more readily available than particulate Fe (PFe). The PFe pool can be separated into a labile fraction, which is potentially transferable to the dissolved phase on time scales relevant to phytoplankton blooms, and a refractory fraction, which is considered biologically unavailable. Seawater samples to determine Fe speciation were collected in spring and early fall of 2013 during three GOA scientific cruises. Trace metal clean procedures were followed during sample collection, processing and analysis. Seawater samples were collected by two methods: 1) Vertical samples were obtained using custom-made samplers (UAF vanes) and filtered offline for PFe analysis; 2) surface samples were obtained by using a towed pump system ("the Fe fish") and filtered in-line for DFe analysis. The PFe fractions of suspended particles were further processed using chemical separation: a) 25 % acetic acid leach with a reducing agent to determine leachable particulate Fe; b) complete digestion of the filter using strong acids to determine refractory particulate Fe. Quantitative determination was by inductively coupled plasma mass spectrometry. Results indicate the broader Western GOA shelf displayed higher average concentrations of total particulate Fe (~121 nM on average) compared to the narrower Southeastern GOA shelf (~18 nM on average). Areas of high glacial input, such as in the vicinity of the Copper River discharge (western side of Kayak Island) and within Prince William Sound near Columbia Glacier, exhibited highly elevated concentrations of total particulate Fe (~430 nM to ~1100 nM). When comparing geographic location, the suspended leachable particulate Fe was higher (~ 22%) over the Southeastern shelf, while the Northern and Western shelf had lower percentage of leachable Fe (11 - 12 %). Over the Southeastern shelf, DFe concentrations were higher in late spring ranging (0.22 - 3.13 nM), while in early fall concentrations were lower (0.07 - 0. 84 nM). Surface water results indicate that there is a significant input of PFe and DFe that occurs in the early fall that extends over much of the Northern shelf and at the inner Western shelf. Variability in downwelling, downwelling relaxation, and upwelling conditions were observed to impact Fe distributions over the Southeastern shelf. These results highlight the impact that the intense environmental variability characteristic of the GOA has on the distribution of Fe species seasonally and geographically.
    • The transport of aerosols into Denali National Park and Preserve

      Wallace, Ashley N. (2012-05)
      Denali National Park and Preserve (DNPP) is a federally protected Class I visibility area in Alaska. The Regional Haze Rule in the U.S. Clean Air Act requires the visibility in all Class I areas to be 'pristine.' According to the EPA DNPP does not have `pristine' air. Therefore, the Alaska Department of Environmental Conservation conducted a 15-month study of particulate matter smaller than 2.5 micrometers (PM2.5) from March, 2008 through June, 2009 to identify the aerosol sources in DNPP. DRUM aerosol impactors collected aerosols at four sites (DNPP Headquarters, Trapper Creek, McGrath, and Lake Minchumina) around DNPP. The aerosol data underwent a series of analyses including: a seasonal analysis of elemental composition, an analysis of potential source regions as identified by the HYbrid Single-Particle Lagrangian Integrated Trajectory ectory (HYSPLIT) model, and Chemical Mass Balance (CMB) analyses to identify specific aerosol sources. These analyses show that the predominant sources of aerosols impacting DNPP during winter and spring lie outside of Alaska and during summer and fall are from outside and local sources. Outside sources include deserts in China and industry in Russia. Because many of the aerosols impacting DNPP are produced internationally, the visibility in DNPP cannot be restored without international collaboration.
    • Vitamin D, cognitive function, and oxidative stress: clues to overtraining syndrome?

      Jerome, Scott P.; Reynolds, Arleigh J.; Duffy, Lawrence K.; Sheppard, Dani K.; Watts, Phillip B. (2018-05)
      Overtraining syndrome (OTS) is characterized by an unexplainable drop in athletic performance. It affects primarily elite, endurance athletes, though sub-elite athletes are also affected. Although the deterioration in performance is often the most pronounced and troublesome symptoms for athletes, others range from severe fatigue and insomnia to depression and lack of mental concentration. There is no known diagnostic tool except for ruling out all other possible explanations for the abnormal performance. The only known remedy for OTS is rest. Some recover within months while others take a year or more. Some athletes never fully recovery and never return to pre-OTS performance levels. The exact mechanism behind OTS is unknown. Consensus has been reached among exercise science professionals that 1) an imbalance between stress load and recovery leads to OTS; 2) OTS exists on a spectrum of possible outcomes from different exercise/rest ratios; and 3) exercise is only one part of systemic stress that can lead to OTS. In addition to physical exercise, other factors such as environmental conditions, family dynamics, schoolwork, job stressors, and social pressures all contribute to the total stress load on the body. A severe and sustained imbalance between stress and rest is a likely contributor to OTS in athletes. I investigated biomarkers and psychological markers that, in concert, could be used to identify athletes who are at the greatest risk for developing OTS before the onset of symptoms. I examined vitamin D, cognitive function, and oxidative stress status in university cross country skiers in addition to athletic performance status during the competitive ski season. This study's results support three primary conclusions. First, collegiate endurance athletes are more prone to vitamin D insufficiency and deficiency than their sedentary counterparts. Second, collegiate cross country ski racers in the circumpolar North are unlikely to maintain adequate vitamin D during a competition season. Furthermore, vitamin D levels are likely to drop in the post-season, recovery period. Third, cognitive function is likely to be significantly higher in the post-season than during the competition season. Fourth, those who experienced a drop in performance during the competition season are more likely to show signs of oxidative stress. These findings may help to produce a screening tool for OTS.